Chairs of the type to which the present invention relates usually have a covering of textile, leather, or the like for the seat and the chair back. The covering, beneath the chair structure itself, is usually padded, for example by foam material or similar padding.
Fashion colors have invaded also the chair, and particularly office chair market. Color combinations which, in the part, were not considered suitable for many conservative offices are now used frequently. Chairs which are used in such offices present problems to manufacturers. It is necessary for the manufacturer to meet demands and products which not only are adequate for the purpose but, additionally, have the appearance and color combinations desired by customers. For minimum cost, mass production and particularly mass production with only few color combinations is desirable; this also permits stocking of only few replacement components or replacement fabric supplies. On the other hand, different color combinations and many more color schemes than previously considered appropriate are now in demand on the market. There is a basic contradiction between minimum costs based on mass production and desire for variety.
Large series mass production reduces manufacturing costs. Use of injection molding is particularly economical if the injection molds can be used over and over again for many different types of chairs. The costs of the molds are high, and large quantities of products must be made from one mold to justify the cost thereof. If one model of a chair does not find market acceptance, or becomes obsolete due to fashion considerations, costs of molds for injection-molded chairs of that type may not be recoverable.
To avoid the costs for molds, it has been proposed to make chair components as deep drawn elements. Deep drawing tools are cheaper than injection molds; yet, the parts made in such processes are inherently more expensive than mass produced injection molded parts.
Different types of chairs present a further problem to the manufacturer. Chairs are made with highly different comfort and appearance characteristics. Chairs are manufactured, for example, in which the seat and the back are fixed with respect to each other; other types of chairs use individually adjustable seats and back rests. Different adjustment mechanisms are also used. A suitable adjustment mechanism which is frequently used permits changing the inclination of the back rest with a simultaneous change of the inclination of the seat and the spacing of the seat from the back rest. Such chairs are also referred to as synchronous chairs, and, as an example, Swiss Patent 524,982 describes and shows such a chair in detail. The back support carrier is formed as a rod which is extended upwardly behind the back; it is bent by about 90.degree. in order to carry the back rest by means of a flange.
U.S. Pat. No. 4,682,814, Hansen, describes a chair in which the back support is formed as a plastic shell which is somewhat L-shaped. The lower portion of the plastic shell is formed laterally with upwardly bent or bowed side walls and surrounds the rearmost portion of the seat. The upper portion of the plastic shell also has bent-up side walls. These side walls laterally surround the upper part of a back support pad located in the upper portion of the plastic shell. The back support pad, consequently, cannot be seen from the rear.
This chair is highly suitable for many applications, but it has been found that, with changing fashions, the cost of making the shells by injection molding becomes very high. If a change in the shape of the shell is desired, a new mold is necessary. The chair has a large visible surface of plastic which, when looked at from the rear, has a somewhat cold or hard impression. It is, therefore, difficult to match the chair to particular requirements dictated, for example, by overall decor of an office, or by interior designers.
The manufacture of chairs of this type has the additional problems that due, to the wide variety of requirements based on comfort and fashion, or designer's specifications, problems arise in connection with stocking and replacement or repair parts. It is customarily expected that a manufacturer of chairs maintains replacement or repair pairs for some period of time, even though a particular chair may have become out of fashion, or out of stock. Storing chair or chair backs is highly space-consuming, and storage costs, particularly for structures of this type with many individual different shapes, interfere with efficient handling, stocking, and long-term and short-term storing; storage requires substantial capital as well as space which, since only infrequently demanded, increases the cost of replacement parts as well as of the initial chairs, and capital therefor could better be used for other purposes.
The chair of U.S. Pat. No. 4,682,814 is particularly useful when applied to the mechanism which results in the synchronous chairs, in which the back rest is formed by a plastic shell. The "plastic look" of the chair, however, may be undesirable and, therefore, it has been proposed to cover the plastic shell with textiles, leather, imitation leather or the like. Covering such a plastic shell is expensive and has the disadvantage that, in spite of the covering, the back of the chair when handled or touched feels "hard".